The Senate on Tuesday backed a prohibition on federal agencies covered under the Commerce, Justice and science appropriations bill from using letters, phone calls or other communications from lawmakers in determining how to spend federal funds.

The amendment, offered by Sen. Jim DeMint (R-S.C.) and approved by voice vote, is the latest in a series of provisions DeMint and other Members have proposed to strengthen the key provisions of the ethics and earmark reform package passed by Congress earlier this year.

With increasing public scrutiny of earmarks, many Members of the House and Senate in recent years have used “phonemarks” to direct federal funding to specific recipients or regions.

Although the White House Office of Management and Budget issued a memorandum earlier this year directing federal agencies to disregard these phonemarks, lawmakers have continued to contact executive branch officials over a variety of projects, according to data collected by the Sunlight Foundation. Additionally, federal officials previously have warned that given the power many of the Members have — particularly those who serve on authorizing or appropriations committees for their agencies — there is enormous pressure on them to comply with these requests.

DeMint argued the changes were needed in large part because of changes to the ethics package eliminating much of the law’s transparency provisions. Congress “pretty much gutted the transparency provisions. We’ve made some progress” in reversing those changes, DeMint said.

He also took aim at his colleagues, arguing that if an earmark is too controversial to either pass Congress or even be openly proposed, Members should not be able to go to agencies for the funding later.

“If politicians can’t get Congress to pass their earmark, they shouldn’t be able to pick up the phone and pressure a federal agency to spend tax dollars on wasteful pork projects,” DeMint said, adding that “federal agencies are supposed to fund projects based on merit, but some politicians use their clout to circumvent this competitive process to force funding to special interests.”

Bill Allison, a senior fellow at the Sunlight Foundation, agreed, arguing the prohibitions on phonemarks are needed in order to keep Congress honest. “One of the big problems with Congress is that they pass rules and then quickly find ways around them,” Allison explained. “Any attempt to cut down on these backdoor ways of getting money to these favored recipients is a step in the right direction.”